U.S. patent application number 11/144161 was filed with the patent office on 2006-12-07 for three-mode continuously variable transmission with a direct low mode and two split path high modes.
Invention is credited to Dan Coffey, Michael C. Sefcik.
Application Number | 20060276294 11/144161 |
Document ID | / |
Family ID | 37402167 |
Filed Date | 2006-12-07 |
United States Patent
Application |
20060276294 |
Kind Code |
A1 |
Coffey; Dan ; et
al. |
December 7, 2006 |
Three-mode continuously variable transmission with a direct low
mode and two split path high modes
Abstract
A powertrain includes a continuously variable transmission
having a starting mechanism, a continuously variable unit (CVU),
and a pair of planetary gear arrangements. The continuously
variable transmission also includes a plurality of torque
transmitting mechanisms which are selectively engageable in
combinations of two to establish a reverse mode of operation
between the starting mechanism and a transmission output shaft, a
low direct mode of operation, an intermediate split mode of
operation, and a high split mode of operation.
Inventors: |
Coffey; Dan; (Howell,
MI) ; Sefcik; Michael C.; (Linden, MI) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21
P O BOX 300
DETROIT
MI
48265-3000
US
|
Family ID: |
37402167 |
Appl. No.: |
11/144161 |
Filed: |
June 3, 2005 |
Current U.S.
Class: |
475/210 |
Current CPC
Class: |
F16H 37/0846 20130101;
F16H 2037/088 20130101 |
Class at
Publication: |
475/210 |
International
Class: |
F16H 37/02 20060101
F16H037/02 |
Claims
1. A powertrain having a three-mode continuously variable
transmission with a direct low mode and two split path high modes
comprising: input means for delivering power to said continuously
variable transmission; a transmission housing; output means for
delivering power from said continuously variable transmission; a
continuously variable unit having an input member continuously
interconnected with said input means and an output member; a first
planetary gear arrangement having a first member continuously
interconnected with said output member, a second member, and a
third member; a second planetary gear arrangement having a first
member continuously interconnected with said second member of said
first planetary gear arrangement, a second member continuously
interconnected with said output means, and a third member; a first
torque transmitting mechanism for selectively interconnecting said
third member with said second planetary gear arrangement with said
transmission housing; a second torque transmitting mechanism
operable to interconnect two of said members of said first
planetary gear arrangement; a third torque transmitting mechanism
operable to continuously interconnect said third member of said
first planetary gear arrangement with said transmission housing; a
fourth torque transmitting mechanism operable to selectively
interconnect said input means and said third member of said second
planetary gear arrangement; and said torque transmitting mechanisms
being operable in combinations of two to establish three forward
modes and one reverse mode between input means and said output
means.
2. The powertrain having a three-mode continuously variable
transmission with a direct low mode and two split path high modes
defined in claim 1 further comprising: said continuously variable
unit being varied from an underdrive condition to an overdrive
condition during said three forward modes of operation.
3. The powertrain having a three-mode continuously variable
transmission with a direct low mode and two split path high modes
defined in claim 1 further comprising: said first torque
transmitting-transmitting mechanism including a two-way frictional
torque transmitting mechanism and a one-way torque transmitting
mechanism; and said third torque transmitting-transmitting
mechanism including a two-way frictional torque transmitting
mechanism and a one-way torque transmitting mechanism.
4. The powertrain having a three-mode continuously variable
transmission with a direct low mode and two split path high modes
defined in claim 1 further comprising: said input means including a
mechanical power source; and a starting mechanism disposed between
said mechanical power source and said input member of said
continuously variable unit.
5. The powertrain having a three-mode continuously variable
transmission with a direct low mode and two split path high modes
defined in claim 4 further comprising: said starting mechanism
including a torque converter and a torque converter clutch; and
said fourth torque transmitting mechanism being connectable between
said mechanical power source and said third member of said second
planetary gear set in series drive relation with said torque
converter clutch and in by passing relation with said torque
converter of said starting mechanism.
6. The powertrain having a three-mode continuously variable
transmission with a direct low mode and two split path high modes
defined in claim 1 further comprising: said first member of said
first planetary gear arrangement being a sun gear member, said
second member of said first planetary gear arrangement being a ring
gear member, and said third member of said first planetary
arrangement being a planet carrier assembly member; and said first
member of said second planetary gear arrangement being a sun gear
member, said second member of said second planetary gear
arrangement being a ring gear member, and said third member of said
second planetary gear arrangement being a planet carrier assembly
member.
Description
TECHNICAL FIELD
[0001] This invention relates to power transmissions and, more
particularly, to continuously variable power transmissions having a
continuously variable unit disposed to operate with a planetary
gear arrangement.
BACKGROUND OF THE INVENTION
[0002] Passenger vehicles in today's market incorporate a power
transmission that has at least three forward ratios, and quite
often, six forward ratios. These power transmissions are utilized
to extend the operating range of the vehicle engine by reusing the
engine speed range as the gear ratio is changed. In order to make
more efficient use of the engine and its speed range, it has been
proposed to employ a continuously variable type transmission
wherein the ratio change within the transmission is continuous over
during a drive range during which the engine speed might be held
constant. For example, the continuously variable transmission
ratios are changed from an underdrive of four to one (4:1) to an
overdrive of point four to one (0.40:1). A step change transmission
utilizing this same ratio spread would require five or six ratio
steps depending upon the step ratio multiplier desired between the
adjacent ratios.
[0003] The continuously variable type transmissions have been
suggested as single mode and dual mode type power transmissions.
Mostly, the transmissions for passenger vehicles have been proposed
as geared neutral type transmission arrangements wherein the ratios
in the transmission can be changed from forward to reverse without
the interchange of friction devices. While these types of
transmissions provide a simplified control system for forward and
reverse, they do have the disadvantage in that a high portion of
the power is recirculated through the continuously variable unit
and the gearing during the vehicle launch operation. This reduces
the transmission output torque, tractive effort, and the overall
efficiency of the transmission during vehicle launch.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide an
improved three-mode continuously variable transmission.
[0005] In one aspect of the present invention, a continuously
variable unit is incorporated in the transmission with two
planetary gearsets to provide a three-mode continuously variable
transmission.
[0006] In another aspect of the present invention, the continuously
variable transmission has a plurality of selectively engageable
torque transmitting mechanisms, which establish the drive modes
within the transmission.
[0007] In yet another aspect of the present invention, the torque
transmitting mechanisms are engaged in combinations of two to
establish a reverse ratio as well as the three forward modes.
[0008] In still another aspect of the present invention, the
reverse mode and the low forward mode are both direct modes having
all of the power passing through the continuously variable unit
prior to being introduced into the planetary gearsets.
[0009] In yet still another aspect of the present invention, two
high forward modes of operation are both split drive modes wherein
a portion of the power from an engine passes through a mechanical
path and another portion of the power passes through the
continuously variable unit.
[0010] In a further aspect of the present invention, at least two
of the torque transmitting mechanisms provide both a one-way drive
torque transmitter and a two-way frictional drive torque
transmitter.
[0011] In a yet further aspect of the present invention, two of the
torque transmitting mechanisms are stationary type torque
transmitting mechanisms, commonly termed brakes, and two of the
torque transmitting mechanisms are rotating type torque
transmitting mechanisms, commonly termed clutches.
DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional elevational view of a powertrain
having a three-mode transmission incorporating the present
invention.
[0013] FIG. 2 is a schematic representation of the powertrain shown
in FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
[0014] Referring to the drawings, wherein like characters represent
the same or corresponding parts throughout the several views, there
is seen in FIGS. 1 and 2 a powertrain 10 having an engine or other
conventional mechanical power source 12, and a continuously
variable ratio transmission (CVT) 14. The CVT 14 includes a
starting device or mechanism 16, a continuously variable unit (CVU)
18, a first planetary gearset or arrangement 20, and a second
planetary gearset or arrangement 22.
[0015] The starting device 16 is shown as a conventional torque
converter 24 and torque converter clutch 26. The torque converter
24 includes an impeller 28, a turbine 30, and a stator 32. The
impeller 28 is continuously connected with the engine 12 through a
flex plate 34. The turbine 30 and torque converter clutch 26 are
drivingly connected through a hub 36 with an input shaft 38. Also
disposed between the torque converter 24 and the flex plate 34 is a
selectively engageable torque transmitting mechanism or clutch 40.
The clutch 40 selectively connects the output of the hub 36 with a
shaft 42.
[0016] The input shaft 38 is drivingly connected with a sprocket
44, which is drivingly connected through a chain 46 with another
sprocket 48. The sprocket 48 is drivingly connected with a variable
diameter sheave or pulley 50, which is a member of the CVU 18. The
sheave 50 is drivingly connected through a conventional flexible
belt 52 with a variable diameter sheave or pulley 54, which is also
a component of the CVU 18. Each of the sheaves 50 and 54 has a
movable half sheave 56 and 58, respectively. These sheaves, as is
well known, are controlled in axial movement by respective
hydraulic motors 60 and 62. As the sheaves are moved axially, the
belt 52 is transported from one diameter along the sheave 58 to
another and likewise transported along the sheave 50 between two
diameters.
[0017] The belt 52, shown in the position A, is at a maximum
underdrive condition which means that the sheave 54 will rotate
slower than the sheave 50. Thus, the input speed from the input
shaft 38 is reduced between the two pulleys. When the belt 52 is in
the position B, the CVU 18 is at a maximum overdrive condition
wherein the pulley 54 rotates faster than the pulley 50, thereby
creating a speed increase or step-up between the shaft 38 and the
pulley 54.
[0018] A planet carrier 64, which is a component of the planetary
gearset 20, is drivingly connected with a hub 70, which is a
component of a rotating type torque transmitting mechanism 72 and
also a component of a stationary type torque transmitting mechanism
74. The rotating type torque transmitting mechanism 72 is a
conventional fluid-operated clutch having an inner hub 76 and a
plurality of friction plates and clutch plates 80 and 82,
respectively, which are splined between the hub 76 and the hub 70,
respectively.
[0019] The clutch is engaged and disengaged through the operation
of a fluid-operated piston 84, which is slidably disposed in a
housing 86 that is secured to the hub 70. Operatively connected
with the housing 86 is a one-way torque transmitting mechanism 88,
which is operative between a transmission casing or housing 90 and
the housing 86 to hold the hub 70 and therefore the carrier 64
stationary in one direction of rotation. The stationary torque
transmitting mechanism 74 is a conventional band type brake which
is operable by a conventional servo system, not shown, and will
when operated hold the planet carrier 64 stationary during both
directions of rotation.
[0020] The hub 76 is secured to or otherwise drivingly connected
with the sheave 54 and a sun gear member 92, which is a component
of the planetary gearset 20. Planetary gearset 20 also includes a
ring gear member 94, which is drivingly connected with or otherwise
secured to a shaft 96. The planetary gearset 20 also includes a
planet carrier assembly member 98, which is comprised of the planet
carrier 64 and a plurality of pinion gears 100 that are rotatable
mounted on the carrier 64 and disposed in meshing relationship with
the sun gear member 92 and the ring gear member 94.
[0021] The shaft 96 is drivingly connected with a transfer gear
102, which is disposed in meshing relationship with a transfer gear
104. The transfer gear 104 is drivingly connected through a shaft
106 through a sun gear member 108, which is a component of the
planetary gearset 22. The planetary gearset 22 also includes a ring
gear member 110 and a planet carrier assembly member 112. The
planet carrier assembly member 112 has a plurality of pinion gears
114 that are rotatably mounted on a planet carrier 116 and disposed
in meshing relationship with both the sun gear member 108 and the
ring gear member 110. Both the planetary gearsets 20 and 22 are
what are termed simple planetary gearsets in that they have a
single set of meshing pinions between the respective sun gear
members and ring gear members.
[0022] The planet carrier 116 is drivingly connected with the shaft
42 and therefore the torque transmitting mechanism 40. The ring
gear member 110 is drivingly connected with a transmission output
shaft 118. The planet carrier 116 is drivingly connected with an
inner race 120 of a selectively operable conventional one-way
torque transmitting mechanism 122. The torque transmitting
mechanism 122 has an outer race 124, which is selectively
engageable with the transmission housing 90.
[0023] As is well known, the selectively engageable one-way torque
transmitting mechanism 122 can be controlled to permit clockwise
rotation while preventing counterclockwise rotation, and likewise
can be controlled to permit counterclockwise rotation while
preventing clockwise rotation. Thus, the planet carrier assembly
member 112 can be restrained from clockwise rotation while
permitting counterclockwise rotation, and also be prevented or
restrained from counterclockwise rotation while permitting
clockwise rotation.
[0024] When the selectively engageable torque transmitting
mechanism 40 is engaged, the planet carrier 116 will rotate in
unison with the flex plate 34 and therefore be rotated at the speed
of the engine 12.
[0025] The planet carrier 116 is connected with the shaft 42
through a hub 126, which is surrounded by a selectively engageable
stationary type torque transmitting mechanism 128. The torque
transmitting mechanism 128 is in the form of a single wrap brake
band, which is selectively operated by a conventional hydraulic
servomechanism, not shown. When the torque transmitting mechanism
128 is selectively engaged, the planet carrier 116 is restrained
from rotation in both directions of operation.
[0026] The controlled engagement of the torque transmitting
mechanisms will control the transmission 14 to operate in a reverse
mode, a first low mode, an intermediate split mode, and a high
split mode. During both the reverse mode and the low mode, the
transmission 14 is in a direct drive condition wherein all of the
power from the engine 12 is transmitted through the CVU 18 while
during both of the high split modes, a portion of the power is
transmitted from the engine 12 to the shaft 42 while another
portion of the power is transmitted through the CVU 18.
[0027] To establish the reverse mode of operation, the torque
transmitting mechanism 74 and the torque transmitting mechanism
128, or in the alternative, the torque transmitting mechanism 122
are engaged. During the reverse mode of rotation, the sun gear
member 92 is rotated in the same direction as the rotation of the
engine 12. The carrier 64 is held stationary therefore the ring
gear member 94 rotates in an opposite direction to the engine 12.
The rotation of the ring gear member 94 is transmitted through the
transfer gears 102 and 104 such that the sun gear member 108
rotates in the same direction as the engine 12. The planet carrier
116 is held stationary resulting in reverse rotation of the output
shaft 118. The speed of the output shaft 118 can be controlled by
controlling the speed of the engine 12 as well as controlling the
ratio of the CVU 18. Generally during operation, the engine 12 is
set at a maximum common speed while the belt 52 is adjusted from
the position A to the position B which results in a speed change
between the engine 12 and the output shaft 118.
[0028] The torque transmitting mechanism 128 is engaged whenever it
is desirable to have engine braking, since the one-way torque
transmitting mechanism 122 will permit the vehicle to coast in the
reverse direction without transmitting torque back to the engine
12.
[0029] The forward low range of operation is established with the
engagement of the torque transmitting mechanism 72 and the
selective positioning of the outer race 124 of the torque
transmitting mechanism 122. The torque transmitting mechanism 128
may also be engaged during the low mode of operation. During the
low mode of operation, the variable sheave 54 and the planetary
gearset 20 rotate in unison. The torque transmitting mechanism 72
assures that this will occur since it directly connects the planet
carrier 64 with the sun gear member 92. The transfer gears 102 and
104 reverses the rotation of the sheave 54 such that the rotation
direction is opposite to that of the engine 12. However, the planet
carrier 116 is held stationary such that the ring gear member 110
and the output shaft 118 rotate in a direction the same as the
engine.
[0030] The output speed in the low mode is controlled by the engine
speed as well as the ratio of the CVU 18. As with the case in
reverse, the CVU 18 begins at the maximum underdrive position A and
progresses toward the maximum overdrive position B, while the
engine speed is held at a constant value. However, if desirable,
the engine speed can be changed during this operation. When the
ratio of the CVU 18 is at the maximum overdrive position B, the
output shaft 118 will be operating at apporoximately the same speed
as the output of the engine 12.
[0031] At this point, the torque transmitting mechanism 40 is
engaged and the one-way torque transmitting mechanism 122 is
disengaged. The torque transmitting mechanism 72 is released thus
causing the one-way torque transmitting mechanism 88 to become
active which prevents forward rotation of the planet carrier 64.
Thus, the sun gear member 92, which is driven by the CVU 18,
enforces reverse rotation of the ring gear member 94 resulting in
forward rotation of the sun gear member 108.
[0032] With the engagement of the torque transmitting mechanism 40,
the planet carrier 116 is driven directly at the speed of the
engine 12. The speed of the output shaft 118 is approximately
constant when shifting between the low direct mode and the
intermediate mode. It is also a double transition shift, that is,
two selectively engageable devices are disengaged while two other
selectively engageable devices are engaged. The use of the one-way
torque transmitting mechanisms provides for a smooth double
transition interchange. During the interchange, the torque
transmitting mechanism 40 is engaged while the torque transmitting
mechanism 72 is disengaged.
[0033] The speed of the output shaft 118 is increased during the
intermediate mode of operation by continuing to change the ratio of
the CVU from essentially a direct drive, which occurred at the
interchange beginning at the overdrive position B and progressing
toward the underdrive position A. When the ratio of the CVU 18
reaches the maximum under drive position A, the transmission is
shifted or has a ratio interchange from the intermediate mode to a
high mode of operation. During the high mode of operation, the
torque transmitting mechanism 72 is engaged and the torque
transmitting mechanism 88 is released. The interchange from
intermediate to high is a nonsynchronous interchange; however, this
interchange is accommodated by the use of the one-way torque
transmitting mechanism 88.
[0034] During the high mode of operation, the planetary gearset 20
is rotated as a single unit resulting in the sun gear member 108
being driven in a direction opposite to the direction of the engine
12. During the high mode of operation, it is again possible to hold
the engine speed at a fixed value while the ratio of the CVU 18 is
changed from a ratio at the interchange toward a further overdrive
condition. As the ratio of the CVU 18 changes toward an overdrive
condition, the speed of the sun gear member 108 is increased in the
reverse direction which will result in an increase of the speed of
the ring gear member 110 and therefore the output shaft 118 in a
positive or engine rotation direction.
[0035] From the above description, it should now be apparent that
the reverse mode of operation and the low mode of operation are
both direct drive modes. That is, all of the power from the engine
is transmitted through the CVU to the output shaft 118. The two
high modes, first the intermediate mode and then the high mode of
operation, are both split path operations wherein a portion of the
power is transmitted directly from the engine through the shaft 42
to the planet carrier 116, and a portion of the power is
transmitted through the CVU 18 to the sun gear member 108. Thus,
the two high modes of operation are split path modes which reduce
the torque transmission through the CVU 18. These split path modes
of operation are more efficient than the direct path mode of
operation.
[0036] It should be noted that the use of the three modes of
operation also provides for a narrow ratio change within the CVU
during any one of the modes of operation. It should now be apparent
to those skilled in the art that during the entire operating
spectrum, the CVU ratio is changing from an underdrive condition to
an overdrive condition, and the speed of the output shaft is
continually increased during this operation.
[0037] Obviously, many modifications and variations are possible in
light of the above disclosure. Therefore, it should be understood
that the invention is only to be limited by the scope of the
appended claims.
* * * * *